Grain Crops

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Dr. Chad Lee

Extension Grain Crops

859.257.3203

cdlee2@uky.edu

Dr. Jim Herbek

Extension Grain Crops

270.365.7541 ext. 205

jherbek@uky.edu

Harvesting Corn for Silage under Drought Conditions

Chad Lee, Grain Crops Extension, University of Kentucky

August 22, 2005

The following are some brief bullet points on harvesting drought-stressed corn for silage. For more information, contact your county extension office.

Why harvest drought-stressed corn for silage

• Drought-stressed corn that is unlikely to resume growth should be ensiled.  Harvesting drought-stressed corn should result in 85 to 100% of the normal net energy content.

• This corn may contain more crude protein than corn harvested under less stressful conditions.

• This corn may contain high nitrate concentrations, especially in the lower third of the plant.

• The ensiled corn should not be fed until at least three weeks after the silo has been filled.

Caution about nitrates

• At high enough concentrations, nitrates are poisonous to cattle. Ensiling reduce nitrate levels by 30 to 50%.

• The University of Kentucky Livestock Disease Diagnostic Center has testing kits available free of charge to county extension offices for testing corn for nitrates. These kits will provide a ballpark estimate for the level of nitrates in the corn before harvest or in the corn after ensiling.

• If the kit indicates a high level of nitrates, then a sample should be sent off for further analysis prior to feeding.

When to harvest drought-stressed corn for silage

• Ideal to harvest when the milk line is ½ to ¾ down the kernel, which occurs during dent stage.

• Leaves above the ear should be mostly green.

• Dry matter content should be near 35%, slightly less for storage in bunkers, trenches, or stacks.

• In drought-stressed situations, the corn kernels may be small, but the milk line will develop quickly.

• Silage should be chopped into lengths of approximately 3/8 to 1/2 inch.

Determining Crop Moisture (Microwave Method)

• This method provides a fairly accurate estimate of crop moisture but requires scales, a microwave, and people who do not mind the smell of burnt corn in the microwave.

• Collect a representative sample of fresh plants.

• Chop the plants in 1 to 2 inch pieces.

• Weight a sample (about 3 to 4 oz or 100 g). This will be referred to as the fresh weight.

• Spread the sample uniformly and thinly over a microwave safe dish and place in microwave oven.

• Heat for 1 to 2 minutes and weigh. Heat for 30 seconds and reweigh. Repeat until two weight recordings are similar. If the sample chars, use the previous weight. This is referred to as the dry weight.

• Calculate the percent moisture. Percent moisture = [(fresh weight – dry weight)/fresh weight] x 100.

Determining Crop Moisture (Grab Test Method)

• This method provides a ballpark estimate of crop moisture.

• Squeeze a handful of green chop as tightly as possible for 90 seconds to make a forage ball.

• If the forage ball holds shape and there is considerable free juice, moisture is above 80%

• If the forage ball holds shape but has very little free juice, the moisture is about 70 to 75%

• If the forage ball falls apart slowly and has no free juice, the moisture is about 70 to 60%, which is ideal for most ensilage situations.

• If the forage ball falls apart rapidly, the moisture is below 60%, making ensilage more difficult.

Harvesting corn for silage increases the risk of lethal gases.

• Lethal gases - greatest danger is between 12 to 72 hours after filling.

• Run the blower.

• Stay out of the silo for at least one week after filling.

• Keep doors closed between silos and barns.

• Any experience of the slightest throat irritation or coughing requires immediate medical attention.

Test the ensiled corn for nutrient quality.

• Collect a couple handfuls of each load of silage that is being unloaded.

• Keep the samples out of sunlight.

• Mix the samples together.

• Keep refrigerated until sent off for analysis.